Neonates are incapable of maintaining their own body temperature during the first few weeks of life. Skin perfusion rates are very high and the infant loses heat rapidly. Thermal management is critical, requiring an accurate, fast, noninvasive method of core temperature measurement.
Rectal temperature has long been considered to be the standard indicator of neonate core temperature. However, since temperature measurements from different locations on a neonate""s skin are sufficiently uniform as to be relatively interchangeable with one another, the clinician may select the most noninvasive and convenient site at which to measure temperature. Due to its inherent safety and long established efficacy, axilla is the most recommended site for neonates. Unfortunately, conventional thermometers such as glass/mercury, electronic and paper strip thermometers require up to several minutes to obtain an accurate axillary reading.
In recent years, infrared thermometers have come into wide use for detection of temperature of adults. For core temperature readings, infrared thermometers which are adapted to be inserted into the patient""s ear have been extremely successful.
Infrared thermometry has not found such high acceptance for use with neonates. Neonates have a very high moisture level in their ear canals, due to the presence of vernix and residual amniotic fluid, resulting in low tympanic temperatures because of the associative evaporative cooling. In addition, environmental uncertainties, such as radiant heaters and warming pads can significantly influence the air temperatures. Further, clinicians are less inclined to position the tip of an infrared thermometer in the ear of a small neonate.
The present invention relates to an infrared thermometer which is designed for axillary temperature measurements. An infrared detector probe is designed to easily slide into the axilla to lightly touch the apex of the axilla. Because it relies on infrared temperature detection, a temperature reading can be obtained in as little as one-half second. A novel cover is also provided to provide for ease of use in a sterile environment.
In accordance with the present invention, a person""s temperature is obtained using an infrared detector having a window through which a sensor views a surface target. A sheet is stretched at least over a portion of the infrared detector, and a tip of the detector is pressed against the person""s skin, with the sheet therebetween, to detect heat flux from the skin. Preferably, the window through which the sensor views a surface target is at the base of a reflective cup.
In a preferred embodiment of the invention, the sheet is a bag which fully covers the infrared detector. The preferred bag is rectangular and open along an edge thereof. A flap at the open edge may be folded over the opening to close the bag about the detector. The bag has a pleat, along an edge opposite to the open edge, which expands to provide depth to the bag. The bag membrane is less than 1.25 milli-inch thick and preferably less than 1.0 milli-inch. The bag is preferably about 4 inches by 7xc2xd inches with a pleat at least xc2xd inch deep, preferably about xc2xe inch.
It is preferred that the sheet which covers the detector is infrared transparent. However, the sheet may be opaque if it is able to quickly equalize in temperature with the target temperature. Thermal equalization is obtained quickly with a thin membrane. Thus, though thicker membranes may be used, it is preferred that the plastic membrane be less than 1.25 milli-inch to allow for prompt temperature equalization. That temperature equalization is even important with a transparent membrane since the detector may still see heat flux from the membrane. With a transparent membrane, it is important that the membrane be kept thin in order to absorb as little infrared radiation as possible passing from the target to the detector and to assure prompt temperature equalization of the membrane with the target.
The preferred detector comprises a main body to be held by hand and a sensor probe. The probe has a first portion extending from an end surface of the main body and a second portion extending from the first portion substantially parallel to the end surface. The top of the second portion and the outer corner where the first and second portions join are rounded. The second portion of the probe has a frustoconical tip which ends at a cup in which the window is positioned. A peripheral bead surrounds the probe behind the frustoconical tip to stretch the transparent bag across the end of the tip. A nub extends from an end surface of the main body opposite to the sensor probe, the nub stretching and retaining the transparent bag.